Download Dance of Earth and Moon

Science Benchmark: 03 : 01
Earth orbits around the sun, and the moon orbits around Earth. Earth is spherical in shape and
rotates on its axis to produce the night and day cycle. To people on Earth, this turning of the planet makes
it appear as though the sun, moon, planets, and stars are moving across the sky once a day. However, this
is only a perception as viewed from Earth.
Standard I:
Students will understand that the shape of Earth and the moon are spherical and that Earth rotates
on its axis to produce the appearance of the sun and moon moving through the sky.
STUDENT BACKGROUND INFORMATION
Dance of Earth and Moon
Think of a time when you were
camping or boating or just out at
night looking at the sky. Suddenly,
you see a very bright, round object
rise in the sky from behind a mountain. This round object not only
lights up the night sky, but it makes
things seem brighter around you.
This object is brighter than the stars
but not as bright as the sun. What is it? Of course, it is the moon.
When viewed from Earth the moon looks like it is
glowing. The moon doesn't make its own light. So,
what makes it shine in the sky? As the sun’s light
shines on the moon, the light bounces off the moon’s
surface to our eyes. Earth does the same thing. If
you were on the moon looking at Earth, you would
see the sun’s light bounce off Earth. In fact, light
bounces off all the planets and moons in our solar
system. That’s how we know they are there.
moon - a natural, rocky object that goes around a planet
Grade
Benchmark
Standard
Page
03
03 : 01
01
8.1.1
Do you think that Earth and the moon have the same appearance, as seen from
space, or do you think they look different? What does Earth look like from space?
You can see the land, the water, and the clouds that surround it in the air. Since Earth
has more water than land, it looks blue. You can also see the thin layer of air that is
around Earth. What do you think the moon looks like from space? You can see that
the moon has hundreds of shallow holes on it made by rocks which fell from space.
You can also see mountains made from
volcanoes and dark patches made by the
lava. Because the moon has no water or air,
it looks light gray from space. How do Earth
and the moon look the same? If you guessed
that they are both spheres, you are correct.
The moon is much smaller than Earth. Earth
appears to be about four times larger than the
moon.
Moon and Earth
Another object we see in our sky each day is the sun. We could not live
without it. Each day we see the sun rise at the beginning of the day and set at the
beginning of the night. However, the sun always stays in the same place. Have you
ever wondered why the sun seems to be moving in the sky? Have you ever wondered
why we have night and day? Look at the picture of Earth on the next page. Since
Earth is round, sunlight can only shine on half of Earth at one time. Earth doesn’t
stay still. Earth rotates or spins around on an axis. This rotation brings the sun into
our view in the morning; we call this a sunrise. As Earth continues to rotate, the sun
seems to move across the sky. Finally, the rotation of Earth takes the sun out of our
view in the evening; we call this a sunset. In a few hours as Earth continues to rotate
the sun will seem to come up again. The time it takes Earth to make a full rotation is
24 hours or one day.
appearance - the way something looks
axis - an imaginary line that goes through the center of a planet
rotatation - the spinning of an object (planet) around its own axis
sphere - round like a ball
8.1.2
Rotation of
Earth
The rotation of Earth brings the sun in and out of view. When the sun is out of
view and it is dark, what do you see in the sky? Yes! Stars appear in the night sky.
Have you ever watched those stars closely at night for a couple of hours? If you have,
you probably noticed that they seem to be moving across the sky. Many stars go in and
out of view like the sun. What do you think is happening? It is the rotation of Earth
that makes them seem to appear to be moving across the sky.
As Earth rotates, causing night and day,
it also takes a long journey around the sun.
This yearly journey is called a revolution.
This revolution takes 365 days, or one
year. Earth follows an orbit on this journey
around the sun.
We can understand these ideas of rotation and revolution better by using a globe
of Earth as a model. Put a lamp with its
shade off in the middle of a room. Turn on
the lamp light. Hold the globe in the air
about ten feet away from the lamp. Spin it.
Earth's revolution
around the Sun.
This represents Earth rotating on its axis.
What do you notice about the light on the
globe? As the globe spins, the light shines on different parts of the globe while other
parts are dark. This model shows how we get night and day from the rotation of Earth.
Remember, Earth rotates on its axis once every 24 hours to produce the night and day
cycle.
model - a small-sized copy of something
orbit - the path an object in space follows as it revolves around another object
revolution - an object in space makes one complete circle around another object in
space
8.1.3
Our model can also show Earth's revolution around the sun. With the globe in
hand, walk around the lamp in a circle, and stop where you started. This represents
Earth's revolution around the sun. It takes Earth about 365 days to go around the sun.
If you were to continue to walk around the lamp in the exact path, this would represent Earth's orbit.
Using the same model, hold a star behind the globe about twenty feet away
from the globe. Now, spin the globe. If we were on the globe, when would we be
able to see the star? What does the star seem to be doing as Earth rotates? As the
globe spins, the star seems to move across the night sky.
Let's find out more about the moon. Possibly you have noticed that sometimes
the moon is up during daylight hours. Sometimes it is up during nighttime hours.
This is because the moon doesn't stay in the same place in space like the sun does.
The moon moves around Earth in an orbit just as Earth moves around the sun. When
the moon has made one complete circle around Earth, it too, has made one full revolution. This revolution takes about twenty-eight days for the moon to orbit Earth.
Earth
Sun
moon
8.1.4
As Earth rotates on its axis, the moon goes in and out of our view each day just
like the sun and stars do. Therefore, the moon seems to rise, move across the sky, and
set. Because the moon orbits Earth, it makes its own schedule when it appears and
disappears from our view each day. Each day we see the moon, it has orbited around
Earth a little more. This makes the moon come up a little later each day.
Make a model of the moon orbiting Earth. With the lamp in the middle or the
room, have a student hold the globe, and have another student revolve slowly around
the globe with a small ball in hand representing the moon. Can you see how the moon
seems to move across the sky after coming into view? As the student with the ball is
revolving around the globe, can you see how sometimes the moon can be seen
during the day and sometimes at night? When the ball returns to the same place it
began, this represents a full revolution of the moon around Earth. Using a model can
help us understand science.
8.1.5
Science Language Students Need to Know and Use
1. appearance: the way something looks
2. axis: an imaginary line that goes through the center of a planet
3. model: a small-sized copy of something
4. moon: a natural, rocky object that goes around a planet
5. orbit: the path an object in space follows as it revolves around another object
6. revolution: one orbit of an object in space around another object in space
7. rotation: the spinning of an object (planet) around its own axis
8. sphere: round like a ball
8.1.6